For now the most massive freeware game for Gameboy Advance were the Uranus series by ZoneGN. This isn’t anymore. At a well known emulation news page, they got a game submission”El-Hazard”. The whole rom is nearly 20 megabytes! This romis officialy declared as game, but it’s probably more an interactive story…oh well, here is a copy and paste of the news from zophars.net, btw a big thanks toGuyfawkesfor the news:

We’re looking at a full-sized (32MB) GBA ROM created in the course of about 2 weeks. This game is essentially”El-Hazard for the GBA”, a 4th port for a game that was seen only on two official platforms; the PC-9821 and the Japan Sega Saturn market. The game, which is based on a mostly cult-followed anime series, never had an English/US release and was pretty much squelched in its own markets. (Rare and very very out of print, although it pops up on eBay every couple weeks or so.)The game itself is nothing fantastic as far as technology goes; it barely used the Sega Saturn’s power. However it has literally hundreds of handdrawn, full-color backgrounds and a dynamic storyline based on a menu driven sort of RPG system.My original project was one of pity when I reverse engineered the Sega Saturn version’s data files to create a Windows PC runtime version (EHPC) which is fully documented here:http://www.el-hazardonline.net/cgi-bin/eholpage.cgi?series=PC;menu=6;content=elhazardpc/elhazardpc.htmlIt’s not just an emulation, but a complete, self-contained engine that runs script files and sprite animation files similar to the original Saturn version. It also has internal ability to use a real El-Hazard Saturn CD-ROM if you own it. The GBA version follows this mostly except of course it has a specific set of controls (A=Advance message, B=Turbo advance, START=Enter Option Menu during a dialog)But enough on that; the GBA ROM version is nearly identical to the PC version. Most of the C source used from the original, save for graphics-specific calls, compiled fairly easily under DevKit Advance with minimal changes. The major losses are mostly in color, since all Saturn graphics were 15-bit, and a bit of resolution.The GBA port runs Mode 4 (256 color bitmap mode) and of course the sprites are 16 or 256 color (GBA hardware limitation).This game is a”full”version, not a demo ROM. It contains the full eight”chapters”of the original Saturn version, fully functional save slots, and all necessary graphics/sounds/music as intact as they will ever be on a GBA. This ROM WILL boot from a real GBA BIOS startup in an emulator (i.e. the header appears to be correct), but so far only runs properly under VirtualBoy Advance. It has only been tested on the PC release of VBA 1.15, though I hope it works on the Mac port as well. It has not yet been tested on real hardware, and I suspect it won’t run without tweaking (but I don’t honestly know and will not know until I get a FlashLinker or related tool). There are still a few minor display bugs and a few technical bugs, but it’s otherwise quite playable AFAIK. I unfortunately didn’t have time to play it through nine times myself to test it every which way (which probably would’ve taken another week at least!)

http://www.zophar.net/